Powder metal gripping elements for settable downhole tools having slips

ABSTRACT

A settable downhole tool with millable powder metal slips having a case hardened edge and a soft core.

This utility application claims priority to, and the benefit of, provisional patent application No. 62/419,214, filed Nov. 8, 2016, and is a continuation-in-part of patent application Ser. No. 15/672,790, filed Aug. 9, 2017. Both of these prior applications are herein incorporated by reference in their entirety.

FIELD OF THE INVENTION

Settable downhole tools having slips for anchoring the downhole tools in a wellbore, the slips having at least one slip button or wicker made of a millable powder metal material.

BACKGROUND OF THE INVENTION

In drilling or reworking oil or gas wells, a number of downhole tools may be used to seal tubing, casing or other pipe. Some of these downhole tools are packers and bridge plugs and may be settable tools with drillable (millable) components made from materials including mild steel, cast iron, plastics, and/or composites. Downhole tools may include slips which hold gripping elements for setting and anchoring the tool against the casing in the wellbore. The gripping elements are often cylindrically-shaped inserts or buttons are often placed in slip bodies that have cylindrical holes or recesses in an outer surface thereof configured to receive the buttons or inserts. The gripping elements may also be wickers.

Gripping elements are held within slip bodies and typically harder than the slip bodies. The primary function of inserts is to dig into and grip the casing to hold the plug to the casing against pressure from above or below the plug. This requires a casing facing outer surface or edge to dig into the casing and a body which is hard enough to support the casing facing outer surface or edge. Some prior art gripping elements are made of carbide, which is hard and meets both requirements. However, hard carbide gripping elements are an impediment to quickly milling out the plug. Some prior art inserts facilitate milling out by having a softer body and an outer surface that is case hardened, capped with harder materials, coated with ceramic materials, or otherwise made harder than the body of the insert. Some prior art inserts have an iron insert body and a relatively harder case hardened outer surface.

U.S. Pat. No. 9,416,617 (Weise et al. 2016) addresses the nature of slips and slip buttons and is incorporated herein by reference. It discloses a tool with a mandrel with sealing elements disposed about the mandrel between the uphole and downhole ends thereof. The '617 patent discloses slips having slip bodies and inserts (buttons). The uphole slips have inserts composed of a ceramic material and the downhole slips have inserts composed of a metallic material including, in some embodiments, a specific powder metal material, namely a sinter-hardened powder metal steel having a balance of iron, and an admixture of carbon and alloy components of molybdenum, chromium and manganese. The '617 patent discloses inserts comprised of a low alloy steel, prealloyed with manganese, chromium and molybdenum for improved strength and hardenability, exemplified by the use of Low Alloy Chromium-Manganese steels, such as FL-5305 HT series, obtaining a higher strength and apparent hardness throughout the insert by use of the added elements (manganese, chromium and molybdenum) and the sintered-hardened (rapid cooling) process. Other patents with disclosures relevant to these issues are U.S. Pat. Nos. 9,273,527; and 9,097,076; each of which is incorporated herein by reference.

SUMMARY OF THE INVENTION

Without limitation, some of this application's described embodiments show inserts with an outer surface hard enough for usefully digging into and gripping the casing and an insert body which is hard enough to support the insert's hard outer surface as it digs into and grips the casing, but which insert body is sufficiently softer than prior art insert bodies to be materially more drillable than prior art insert bodies. Some of the embodiments described herein produce faster milling out of plugs having the inserts as taught herein than plugs having similarly sized, shaped, and placed prior art inserts. Additionally, the inserts of some of the embodiments described herein leave less production interfering debris than similarly sized, shaped and placed prior art inserts of similar plugs.

It is believed that plugs having inserts of some of the embodiments described herein may be milled out in 25% of the time it would take to mill out a similar plug with carbide or other prior art inserts. Additionally it is believed that, plugs having inserts as some of the embodiments described herein may be milled out in 50% of the time it would take to mill out a similar plug with carbide or other prior art inserts. Additionally, it is believed that plugs having inserts of some of the embodiments as described herein may be milled out in 75% of the time it would take to mill out a similar plug with carbide or other prior art inserts.

It is believed that plugs having inserts of some of the embodiments as described herein may be milled out in less than 10 minutes using typical milling methods in typical wells as are known in the art. Additionally, plugs having inserts of some of the embodiments herein may be milled out in less than 20 minutes using typical milling methods in typical wells as are known in the art.

It is believed that plugs having inserts of some of the embodiments described herein may leave 50% less production interfering debris after the plug is milled out than is left after milling out a similar plug with carbide or other prior art inserts. Additionally, plugs having inserts of some of the embodiments described herein may leave 25% less production interfering debris after being milled out than is left after milling out a similar plug with carbide or other prior art inserts. Additionally, plugs having inserts of some of the embodiments as described herein may leave 10% less production interfering debris after being milled out than is left after milling out a similar plug with carbide or other prior art inserts.

It is believed that the hardness of insert bodies of some of the embodiments as described herein may be 50% less hard than the hardness of carbide or other insert bodies of similar inserts in similar plugs which are capable of being set in a casing and holding the plug against equivalent pressure on the plug. Additionally, the hardness of insert bodies of some of the embodiments as described herein may be 30% less hard than the hardness of insert bodies of carbide or other similar inserts in similar plugs which are capable of being set in a casing and holding the plug against equivalent pressure on the plug. Additionally, the hardness of insert bodies of some of the embodiments as described herein may be 20% less hard than the hardness of insert bodies of carbide or other similar inserts in similar plugs which are capable of being set in a casing and holding the plug against equivalent pressure on the plug.

It is believed that for inserts of some of the embodiments as described herein, the hardness of the casing facing outer surface of the inserts may be in the range of 70-97 HR15N hardness, or in the range of 75-90 HR15N hardness or preferably in the range of 85-90 HR15N hardness. It is believed that for some of the embodiments described herein the hardness of the core of the insert body is in the range of range of 12-60 HRB hardness or 17-50 HRB hardness or preferably in the range of 17-40 HRB hardness.

It is believed that for inserts of some of the embodiments as described herein, the difference between the hardness of the middle of the insert's body, measured by sectioning the insert's body and testing it, and the hardness of the insert's casing facing outer surface is that the insert's body is more than 60% softer than its outer edge. Additionally, it is believed that or some of the embodiments described herein the difference between the hardness of the middle of the insert's body and the hardness of the inserts casing facing outer surface is that the inserts body is more than 50% softer than its outer edge. Additionally, for some of the embodiments described herein it is believed that the difference between the hardness of the middle of the insert body is more than 25% softer than its outer edge. Case hardening or other hardening of the gripping element's outer layer by the methods taught herein extends its hardening effect somewhat into the gripping element, the hardening of the compacted powdered metal being lessened proceeding from the outer surface to the center of the gripping element. Accordingly, the gripping element will have a gradient of hardness measurements taken from one side of the gripping element to the other side of the gripping element the softest portion being in the middle of the gripping element. The hardness measurements of the core stated herein are measurements of the center of the gripping element, the softest center of the core.

A useful result of beginning with a very soft metal insert substrate as described in some of the embodiments herein and case hardening it, such as by nitriding, carbonitriding or carburizing the compacted powdered metal to produce an insert having a hard outer layer and a very soft core, is that the resulting insert has some of the characteristics of an egg shell; very hard on the outside and very soft on the inside. This is particularly true because the case hardening effect on a soft insert substrate extends somewhat beyond the insert's immediate outer surface. The outer layer is hardened by a process which produces a gripping element having graduated hardness, hardness being inversely correlated to distance from the outer layer, and hardness of the core being materially unaffected by the hardening process. It is believed that the case hardened outer layer of an insert is supported by the somewhat hardened but less hardened area of the insert immediately below the outer layer, which is supported by the immediately below by the somewhat hardened but much less hardened area immediately below it etc., the hardening effect diminishing from the outer layer of the insert toward the center of the insert. The described hardening process produces inserts with graduated support/softness from the hard outside layer in, providing an egg-type structure whose hard outer shell is supported enough by the immediately graduated hardness insert to be strong enough to bite into and hold the casing when the tool is set in the casing; but, analogous to an egg with a soft core, such an insert once broken by the mill during milling out is quickly milled into tiny pieces that do not interfere with production.

It is believed that this graduated hardening of the insert toward the outer layer, and reciprocal softening of the insert toward the core, facilitates both of the millable insert's inconsistent purposes, (1) to be hard enough to dig into, grip and hold to the casing and (2) to be quickly and easily millable into small pieces which will not interfere with production. The gripping element is hardened by a process which produces a gripping element having graduated hardness, the hardness of succeeding gripping element layers being inversely correlated to each layer's distance from the outer layer, the core being the softest portion of the gripping element; The somewhat hardened the insert area immediately below the insert's outer layer supports the hard insert's outer layer as the tool is set within the casing and the outer layer digs into or engages the casing. The insert's very soft inner core facilitates easy milling out of the insert. As the mill breaks the insert's outer layer, milling the broken insert is analogous to milling an egg with a broken hard outer shell with a very soft center. The soft inner core facilitates milling out of the insert producing much smaller and lighter debris than similar inserts having a harder core. It is believed that these processes and effects apply in some of the disclosed embodiments, whether the gripping element is a wicker or other gripping structure. These differences relative to the prior art may be materially advantageous.

Some embodiments of this invention relate to downhole tools for use in oil and gas wellbores and more particularly, to tools having drillable (millable) or dissolving/degrading components made from metallic or non-metallic materials, and tools having gripping elements comprising buttons or wicker pads incorporated into slip bodies or full bodied wicker slips, the foregoing being comprised partly or wholly of powder metal (“PM”); in some embodiments, case hardened PM; in some embodiments, case hardened low/no carbon non-alloyed iron; in some embodiments, case hardened by carbonitriding or carburizing. The slip or slips allow for setting and anchoring of the downhole tool, such as packers, frac and bridge plugs used in wellbores.

Buttons used in slips are of sufficient durability and hardness to partially penetrate and bite into the inner surface of the casing to hold the tool to the casing during pressurization, such as during fracing. However, the buttons, in some embodiments, may be constructed of materials that may be easily millable or drilled out once the operation using the tool is finished. The buttons should not be so hard or so tough to that they provide too much resistance to drilling or too much damage to the cutting surfaces of a milling bit. While some prior art buttons provide good bite into the inner wall of a wellbore tubular, they may do so at the expense of easy of drilling and damage to the milling bit.

Applicant discloses, in some embodiments, the use of no/low carbon PM iron buttons, or wicker pads or full bodied wickers, without alloying the iron with other materials, typically ferritic in structure, soft and ductile at its core. The gripping elements may be “as-sintered” then subject to nitriding for creating a hard “shell” or case or layer about a softer interior.

Nitriding and carbonitriding are two technologies which Applicant may use for powder metal surface hardening. Nitriding a metal part such as a PM button or wicker pad may form a hard case or surface layer that partially extends inward. Nitrides or nitrocarbides may provide good frictional and anti-corrosive properties as well as provide good surface hardness, while leaving the body or core of the button less hard.

One type of PM material used by Applicant is MPIF/ASTM F-0000 (standard powder metal materials are defined in North America by MPIF standard 35 and ASTM B783). F-0000 is iron with a 0% (no carbon) up to a maximum of 0.3% by weight carbon (low carbon), and may be ferritic in structure, soft, ductile and magnetic.

The properties of F-0000 are (as sintered):

-   -   Tensile strength (ksi): about 25-38     -   Yield strength (ksi): about 18-25     -   Elongation (%): about 2-7     -   Unnotched impact energy: (ft.-lb.): about 6-35     -   Apparent hardness: about HRB 60-80 HRF     -   Photomicrographs (see FIG. 6A) show the different grain         structure between no carbon (ferritic         structure)/chromium/manganese steels (Martensitic).

There are four main alloying methods for ferrous PM materials and in one manner of classification; the PM materials may be classified by one of these four manners. Admixed—the alloying additions are made to the iron powder base in the form of elemental or ferro alloy powders. The iron powder base is unalloyed when the mix is pressed. Partially alloyed (diffusion alloyed)—the alloying additions are diffusion alloyed to the iron based particles such that the compressibility of the base iron is essentially retained. Pre-alloyed, the alloying elements, except for carbon are added to the meld before atomization. This results in homogeneous microstructures in uniform hardness even on a micro-indentation hardness level. Hybrid alloys—with the advent of highly compressible pre-alloyed powders, materials have been developed based on additions to these powders.

Many PM parts are heat treated in a secondary operation, to develop a tempered Martensitic microstructure either in a surface layer or throughout the part. The need for a secondary quenching operation may be avoided by “sinter hardening” the parts. PM materials with sufficient hardenability will develop microstructures containing significant percentages of Martensite in the as sintered condition. Accelerated cooling techniques for sintering furnaces have been developed which permit larger parts to be sinter hardened or materials with lower hardenability to be used to produce sinter hardened parts.

The compositions of powder metal inserts vary and may include: carbon, copper and nickel steels; phosphorus steels; low alloy molybdenum—nickel steels; low alloy chromium manganese steels; ferritic stainless steel; austenitic stainless steel; martensitic stainless steel; duplex stainless steel; soft magnetic iron-based alloys; high density (FD) tool steel; engineered porosity (EP) grades and custom blends (see www.ssisintrep.com/materials). Carbon, cooper and nickel steels may be designed for light to moderate loading and ease of machinability, ease with which they may be pressed to moderately high densities and their ability to be sintered effectively in a variety of atmospheres. They may be used in gears, pinions, sprockets and other automotive, motorcycle, lawn or garden or other industrial markets.

Sintering is a heat treatment applied to a powder metal compact button to impart strength and integrity. The temperature used for sintering is below the melting point of the major constituent of the powder metallurgy material. After compaction, neighboring powder particles are held together by cold welds, which gives the compact sufficient “green strength” to be handled. At sintering temperature, diffusion processes cause nets to form and grow at these contact points. Prior to solid state sintering, the removal of the pressing lubricant by evaporation and burning of the vapors and the reduction of the surface oxide from the powder particles in the compact is done. These two steps and the sintering process itself are generally achieved in a single, continuous furnace by careful choice and zoning of the furnace atmosphere and by using an appropriate temperature profile. In sinter hardening, a sintering furnace is used that will apply an accelerated cooling rate in the cooling zone. Material grades have been developed that can transform to Martensitic microstructures at these cooling rates. This process, together with a subsequent tempering treatment, is known as sinter hardening and is a process which enhances sintered strength.

Powder metal or powder metallurgy can reduce or avoid the need for metal machining or other metal removal processes and may reduce yield losses in manufacturing. The PM process generally consists of three basic steps: powder blending, die compaction and sintering. Compaction may be formed at room temperature and sintering is usually done under a carefully controlled atmosphere composition and may involve coining or heat treatment. Powder compaction is the process of compacting metal powder in a die to the application of high pressures. Powder metal steel applications are widely employed within the motor industry, for example, in making oil pump gears, rocker arm functions, valve seat inserts, etc. Applications of powder metal parts may reduce energy and material needs.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are isometric views of slips having a slip body and button inserts.

FIG. 2 is a partial cross-sectional view of a settable downhole tool embodying Applicant's slips and inserts.

FIGS. 2A and 2B are a cross-sectional view through a slip (2A) and an external view (2B). The slip has a slip body and inserts or buttons.

FIGS. 3A, 3B, 3C, 3D, 3E and 3F are views of an embodiment of a slip having a slip body with Applicant's PM inserts for use in a settable downhole tool.

FIG. 4 is another embodiment of a settable downhole tool having Applicant's novel slips.

FIGS. 5A, 5B, 5C and 5D are all views of the PM insert or button for use in a slip.

FIG. 6A is a photomicrograph of a section of F-0000 (200X) as—sintered showing ferritic structure.

FIGS. 7A and 7B illustrate a slip comprising a slip body with PM wicker pads (in some embodiments, case hardened) engaged therewith.

FIGS. 8A and 8B illustrate another embodiment of a slip having a PM wicker pad. FIG. 8C illustrates a second embodiment of a PM wicker pad.

FIGS. 9A and 9B illustrate a full body slip, which may be case hardened PM according to the disclosures set forth herein.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Powder metal (“PM”) parts may be heat treated in a number of ways. The heat treatment may include the following: austenitizing; quenching; tempering; normalizing; case hardening; gas nitriding; carburizing; local hardening; induction; flame and laser.

Case hardening is the process of hardening the surface and a region close to the surface of a metal object, including Applicant's powder metal gripping elements, allowing the metal underneath to remain soft, thus forming an outer layer of harder metal (sometimes called the “case”) at and near the surface. Case hardening may involve infusing additional carbon or other material (such as nitrogen) into the surface layer. It may be done after the part is formed into its final shape typically through compaction and sintering.

Mild steels with a low carbon content, usually up to or less than about 0.3%, may have their surface modified chemically to increase the hardness or hardenability. Case hardened steel and some embodiments of Applicant's PM gripping elements may be formed by diffusing carbon (carburization), nitrogen (nitriding), both (carbonitriding) and/or boron (borizing) into the outer layer of the steel or ferrite at a high temperature and then heat treating the surface layer to the desired hardness. Other approaches to case hardening are possible if other alloys are used. Alloys with a martensitic phase can be heat treated for case hardening by flame, laser, induction or other heat-related hardening methods followed with a quench. Ceramic coatings may also have a similar effect.

Carbonitriding is a surface modification of powder metal that increases the surface hardness of the metal, and may reduce wear. Carbonitriding diffuses nitrogen and carbon into the case of the PM gripping elements, below the critical temperature, typically approximately 650° C. Under the critical temperature, the microstructure does not convert to an Austenitic phase, but stays in the ferritic phase, thus the term ferritic nitrocarbonization. Atoms of nitrogen and carbon diffuse into interstitially into the metal at the surface, and slightly or part of the way into the body of the metal, thereby creating a layer of increased hardness and strength near the surface. In some embodiments, the hardened layer of the carbon nitrided parts including gripping elements ranges from about 55-62 HRC at the surface (in another range 40-80 HRC), or a minimum of about 50 HRc, and the non-surface areas softer, in one embodiment, less than a hardness on the HRc scale. In some embodiments, about 75 HR15N or in the range of 70 to 97, specified Rockwell 15N.

Carbonitriding is similar to gas carburization with the addition of ammonia to the carburizing atmosphere, which provides a source of nitrogen. Nitrogen is absorbed into the surface and diffuses into the workpiece along with carbon. In some cases, carbonitriding may be carried out at about 850° C. It is typically carried out at a higher temperature than nitriding (about 530° C.) but slightly lower than those used for carburizing (around 950° C.) for shorter times. Carbonitriding may reduce distortion during quenching. Carburizing is like carbonitriding but without the addition of nitrides. Carbonitriding may form a hardened layer or case that may be between about 0.07 mm to 0.5 mm thick or thicker (inward from the button surface) and generally has a higher hardness than a carburized case. In another embodiment, the hardened layer may be about 0.005″ to 0.040″ thick. A hardened case increases the wear life of the part. Carbonitriding alters the top layers or outer surface of the button and typically does not deposit an additional layer, so the process typically does not alter the dimensions of the part. Carbonitriding may be combined with carburizing for deeper case hardened depths.

FIGS. 5A, 5B, 5C and 5D illustrate applicant's PM insert or button 510. Insert or button 510 is typically cylindrical and may have a top surface 510 a, sidewalls 510 b, bottom surface spaced apart from the top surface bottom surface 510 c (see FIG. 5A). The top surface may be flat in some embodiments. Top edge 510 d may be a trailing edge or a leading edge in some embodiments, depending upon the angle, if any, at which the top surface 510 a makes with the outer surface of the slip, see FIG. 2A for example, lead line 510 d pointing to leading edge. Button 510 may have an outer surface 600 comprising part or all of top surface, side walls and bottom surface. In Applicant's button 510, inner core 604 has properties, including hardness, which are different than outer hardened layer 606. Hardened layer 606 typically includes outer surface 600 and extends partly inward towards the core. Core 604 may in one embodiment be less hard and/or ductile as compared to hardened case. It may also have lower tensile strength and yield and higher elongation.

In one embodiment, PM button 510 or other PM gripping element (see FIGS. 7C, 8C, and 9) starts with a PM workpiece (in some embodiments, comprising iron with 0.3% or less than 0.3% C having the properties (as sintered) set forth above with respect to F-0000 above) and is compacted and treated such that the workpiece, following the sintering process is provided with a hardened layer 606. Hardened layer 606 (see FIGS. 5B and 5D) is typically the result of a post sintering process or processes which leave a core 604 with substantially the same properties of the workpiece as sintered, but leave a hardened layer. In one embodiment, there is either no carbon “as sintered” or low carbon “as sintered,” but carbon is added in the hardened layer during carbonitriding or carburizing. In another embodiment, the maximum carbon before carbonitriding is 0.3%. In one embodiment, the hardened layer has a minimum of about 50 HRc, whereas the core is substantially softer, in some cases not even on the “C” scale. The interior of the button is left soft for easy mill-up and to allow the button to deform under load instead of shattering. But the hardened layer provides excellent bite, even in hard casing.

Settable downhole isolation tool 500 (see FIGS. 2 and 4) may be used with a bridge plug, packer, or frac plug or for any other suitable isolation tool. In one embodiment, tool 500 uses drop ball 432 which may be degradable or non-degradable (see FIG. 2). Conventional setting tools having setting rods are known in the art. FIGS. 2, 3A-3F and 4 illustrate components of or a settable downhole tool 500 in one embodiment with at least some of its elements or parts made of a dissolvable polymer, in one embodiment, a dissolvable polyglycolic acid polymer (for example, a polymer comprising at least in part a PGA (polyglycolic acid) or PLA (polylactic acid) polymer acid. One embodiment, the polyglycolic acid is Kuredux® by Kureha. In another embodiment, the dissolvable elements or parts are made from degradable PGA or PLA or other degradable polymeric materials, such as described in PCT/JP2014/083843, and published Jul. 2, 2015 incorporated herein by reference. In another embodiment, the dissolvable polymer acid polymer is polylactic acid.

Settable downhole tool 500 may also have dissolvable metal alloy and/or polymer acid elements in the same tool or may be a tool comprised at least in part by millable metallic and/or millable composite materials.

Slips, one or both, can be made, at least in part, from a non-metallic material, such as plastic, a molded phenolic, comprising, a laminated non-metallic composite, an epoxy resin polymer with a glass fiber reinforcement, UHMW, PTFE, etc. The novel case hardened PM metal buttons may be combined with buttons made of other material, such as Cermet, zirconia, alumina carbide, and the like on slips of the same tool.

FIG. 2 illustrates downhole tool 500 which includes a mandrel which is the central support element for entraining elements on the outside of downhole tool as described herein and for receiving a setting rod (not shown) on the inside or inner bore of the downhole tool. Load ring 502, if used, may be entrained on the outer surface of mandrel and is adapted to receive the setting tool's sleeve to set downhole tool in ways known in the art. Slips 504/505 (typically two, an upper and lower, maybe only one) may be above and below cones 528 and 529. Set screws may be used to retain cones 528/529 in engagement with the mandrel 414 and may be of conventional design and conventional materials or degradable materials. Center or packing element 526 is typically between the cones as shown in FIGS. 2 and 4.

An optional shear sub may be used to engage mandrel and threadably receive the lower end of the setting rod 506 on its internal threads. A setting rod may pull shear sub 430 upward. The vertical compression pushes slips 504 and 505 and center sealing element 526 outward against the inner wall of the casing. Slips 504 and 505 move outwardly and bite into the casing and central element sealingly compresses against the casing during setting downhole tool.

Slips 504 and 505 in settable downhole tool 500 may be made of a body 508 with Applicant's PM buttons or inserts 510 or wicker pads 706/708. Body 508 may be comprised of any suitable material sufficient rigidity and strength and hold downhole tool 500 against the casing during setting and isolation functions. Body 508 may be comprised of degradable metal having sufficient rigidity and strength sufficient to hold inserts 510 and press them into a biting engagement with the casing sufficient to hold downhole tool 500 against the casing during setting and isolation functions. Inserts 510 may be conventional or similar in shape and size to prior art buttons or inserts.

FIGS. 3A-3F provide additional details concerning the design and construction of slips 504 and 505. A suitable metallic or non-metallic, degradable or millable body 508 includes buttons or inserts 510, in a preferred embodiment, PM inserts as disclosed herein. Slip leading edge 512 of slips 504 and 505 may include multiple grooves 514 (see FIG. 3D) which grooves are partially cut through from leading edge 512 to trailing edge 515. Slips 504 and 505 may separate along their grooves during setting. Tapered inner walls 516 and non-tapered inner walls 518 operate in conjunction with the setting, load ring, and cones in ways known in the art. Some or all of the buttons may comprise hardened PM (carbide, cast iron, etc.). The slips may have some buttons of different dimensions or shapes.

In the Figures and description set forth above, a gripping element is a powdered metal button, in some cases, case hardened by carbonitriding or carburizing is shown engaged with and as part of a slip body, which may be made from any material, drillable or non-drillable or decomposable, or any other material or design known in the art. In the figures that follow, gripping elements comprising wicker pads or wicker segments are shown engaged with a slip body to form a slip that has powder metal wicker pads engaged therewith. Slip 700 in FIGS. 7A, 7B, 8A, 8B, and 8C comprises slip body 702/704 and wicker pads 706/708. Unlike the buttons, wicker pads 706/608 have teeth. Slip body 702 illustrated in the FIG. 7 series is configured with a “T” shape slot for receipt of wicker pads 706, which includes a pair of arms 711 extending from a slip body 714 that includes teeth thereon.

In the FIG. 8 series illustrations, slip body 704 is configured with a non-slotted side wall, which may be canted dovetailed, and slip pad 708 may have dovetailed side walls 713 (see FIG. 8C). Moreover, slot 718 in slip body 704 may be opened at one end and closed at the other.

Both slips 700 having wicker pads 706/708 are configured such that when the wicker pad is inserted into the slip body or otherwise engages the slip bodies 702/704, the teeth of the slip pad extend outside of the outermost wall surface of the slip body, so as to engage the casing when set (see FIGS. 8A and 8B). Both wicker pads and buttons may engage the slip bodies by a snug interference fit and/or an adhesive, such as an epoxy. As part of a tool, in some embodiments, these gripping elements comprise an upper and lower slip—both having the same hardness, dimensions, and composition.

Wicker pads 706/708 may be treated for case hardening by any method known in the art, including the methods set forth herein. Wicker pads 706/708 or other wicker pad configurations may be comprised of any metal alloy, steel, pure iron or low carbon iron. Wicker pads 706/708 may be comprised of a material harder than the casing, such as a material in the hardness range of 40 to 80 HRC. FIG. 8A shows the wicker pads may have a softer core 606 and a harder outer layer 604.

FIG. 9A is a Figure from U.S. Pat. No. 8,496,052 (FIG. 3 in that patent, which patent is incorporated herein by reference) and shows a settable downhole tool 10, which has a gripping element comprising a full body wicker 48 (upper) and 50 (lower), meaning the slip body is not separate from the gripping elements (here, wicker with teeth 49) as in previous embodiments with buttons or wicker pads. Applicant provides the structure illustrated, that is, a wicker shaped the same or similar to those illustrated in FIGS. 9A and 9B, but made from PM with the PM structure, material, and hardness ranges as set forth herein. Here, full body slip is comprised of any metallic material (including those metallic materials disclosed herein and any metal or metal alloy set forth in the prior art), and case hardened in any way disclosed herein. Other non-slip elements illustrated in FIG. 9A are: mandrel 20, piping or casing string 104, wedge elements 46, and teeth 49. FIG. 9B shows how the full body wicker may have softer core 606 with an outer hardened layer 604. The hard outer layer of the full body wicker and wicker pads may be in the thickness ranges disclosed for the buttons or any other effective range.

In one embodiment a settable downhole tool comprises a mandrel; and a slip located about the mandrel for engaging a casing and holding the tool to the casing; wherein the slip is comprised of a unitary body having multiple gripping elements on the slips outer surface; wherein: the slip is made from compacted powdered iron having up to 0.3% by weight carbon, and has an outer layer and a core, the outer layer is for engaging the casing and has been case hardened by nitriding, carbonitriding or carburizing to be harder than the core and has a hardness in the range of 70-97 HR 15 N (superficial Rockwell); the core is for supporting the outer layer against the casing and has hardness in the range of 12-60 HRB (Rockwell); and the slip has one or more relatively thin sections which extend from the upper end of the slip to the lower end of the slip for preferentially breaking at the thin sections as the slip is expanded when the tool is set in the casing.

In an embodiment, the settable downhole tool comprises a mandrel; and a slip located about the mandrel for engaging a production casing and holding the tool to the casing; wherein the slip is comprised of one or more slip bodies and multiple gripping elements, the slip bodies holding the gripping elements; at least some of the gripping elements are: made from compacted powdered iron having up to 0.3% by weight carbon, and have an outer layer and a core, the outer layer is for engaging the casing and has been case hardened by nitriding, carbonitriding or carburizing

to be harder than the core and has a hardness in the range of 70-97 HR 15 N (superficial Rockwell); and the core is held by a slip body, is for supporting the outer layer against the casing, and has hardness in the range of 12-60 HRB (Rockwell); and the tool, after being set in the production casing, may be milled out of the production casing in 50% or less time than needed to mill out a similar tool in which of the similar tool's gripping elements are carbide. In an embodiment, the gripping elements have up to 0.2% by weight carbon. In an embodiment, the gripping elements have up to 0.1% weight carbon. In an embodiment, the gripping elements are substantially 0% by weight carbon. In an embodiment, the gripping elements are an iron alloy and are nearly pure iron. These carbon amounts and ranges are for the gripping element as compacted and before hardening. In some hardening processes, such as carbonitring, carbon may be added, especially to the outer layer. This does not affect the carbon chemistry between the case depth of the PM component. In an embodiment, the gripping element is pure iron rather than an alloy. Carbon is dealt with in the manufacturing and end result gripping element as in an impurity to be minimized, rather than as an alloying agent. In contrast, some prior art inserts may target a minimum concentration of carbon to create a resultant target alloy gripping element.

Applicant believes that making the gripping elements from an alloy of nearly pure iron, and hardening the outer layer of the inserts as described herein, provides inserts with a hard enough outer layer which is sufficiently supported to grip the casing during setting, and whose internal hardness is so low that milling the inserts out is quick and easy, and produces very small cuttings which did not interfere with production. This is true whether the gripping elements are buttons or wicker pads. In an embodiment, upon milling the tool out of the production casing, the largest 10% of the cuttings produced by the milling are at least 30% smaller than the largest 10% of the cuttings produced by milling out a similar tool with carbide inserts under similar conditions.

In an embodiment, a method of making the settable downhole tool comprises: providing a mandrel; providing a slip for being located about the mandrel for engaging a production casing and holding the tool to the casing; wherein the slip is comprised of one or more slip bodies and multiple gripping elements, namely, wickers or inserts, the slip bodies holding the gripping elements; providing at least some gripping elements manufactured from a single material; namely compacted powdered iron with up to 0.3% by weight carbon, and have an outer layer and a core, the outer layer being for engaging the casing and has been hardened by nitriding, carbonitriding or carburizing to be harder than the core and have hardness in the range of 70-97 HR 15 N (superficial Rockwell); and the core is held by a slip body, is for supporting the outer layer against the casing, and has hardness in the range of 12-60 HRB (Rockwell); and assembling the mandrel, slip and gripping elements to make a tool which may be milled out of the production casing in 50% or less time than needed to mill out a similar tool in which of the similar tool's gripping elements are carbide.

The present invention is adapted to attain the ends and advantages mentioned as well as those that are inherent therein. The embodiments disclosed above are illustrative only, as the present invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. No limitations are intended to limit the details of construction or design shown, other than as described in the claims below. The illustrative embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the present invention.

The terminology used herein is for the purpose of describing particular implementations only and is not intended to be limiting. The singular form “a”, “an”, and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises” and/or “comprising,” when used in the this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups therefore. Compositions and methods described in terms of “comprising,” “containing,” or “including” various components or steps, can also “consist essentially of or “consist of the various components and steps.

Whenever a numerical range with a lower limit and an upper limit is disclosed, any number and any included range falling within the range is specifically disclosed. Every range of values (of the form, “from about a to about b,” or, equivalently, “from approximately a to b,” or, equivalently, “from approximately a to b”) disclosed herein is to be understood to set forth every number and range encompassed within the broader range of values. The terms in the claims have their plain, ordinary meaning unless otherwise explicitly and clearly defined by the patentee. If there is any conflict in the usages of a word or term in this specification and one or more patent(s) or other documents that may be incorporated herein by reference, the definitions that are consistent with this specification should be adopted.

The corresponding structure, materials, acts, and equivalents of all means or steps plus function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description is presented for the purposes of illustration and description, but is not intended to be exhaustive or limited to the implementations in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the disclosure. The implementations were chosen and described in order to explain the principles of the disclosure and the practical application and to enable others or ordinary skill in the art to understand the disclosure for various implementations with various modifications as are suited to the particular use contemplated. Those skilled in the art will readily recognize that a variety of additions, deletions, modifications, and substitutions may be made to these implementations. Thus, the scope of the protected subject matter should be judged based on the following claims, which may capture one or more concepts of one or more implementations.

Although the invention has been described with reference to a specific embodiment, this description is not meant to be construed in a limiting sense. On the contrary, various modifications of the disclosed embodiments will become apparent to those skilled in the art upon reference to the description of the invention. It is therefore contemplated that the appended claims will cover such modifications, alternatives, and equivalents that fall within the true spirit and scope of the invention. 

1. A settable downhole tool comprising: a mandrel; and a slip located about the mandrel for engaging a casing and holding the tool to the casing; wherein the slip is comprised of one or more slip bodies and multiple gripping elements, the slip body or slip bodies holding the gripping elements; at least some of the gripping elements are comprised of compacted powdered metal and have an outer layer and a core, the outer layer for engaging the casing and being case hardened to hardness in the range of 70-97 HR 15 N (superficial Rockwell); and the core supporting the outer layer and having hardness in the range of 12-60 HRB (Rockwell); and wherein the tool, after being set in the casing, may be milled out of the casing in less time than needed to mill out a similar tool in which of the similar tool's gripping elements are carbide.
 2. The tool of claim 1 wherein the hardness of the core is in the range of 17-50 HRB.
 3. The tool of claim 2 wherein the hardness of the core is in the range of 17-40 HRB.
 4. The tool of claim 1 wherein the compacted powdered metal is iron with up to 0.3% by weight carbon before the outer layer is hardened.
 5. The tool of claim 1 wherein the compacted powdered metal is iron with up to 0.1% by weight carbon before the outer layer is hardened.
 6. The tool of claim 1 wherein the outer layer is hardened by a process which leaves the hardness of the middle of the core materially unaffected.
 7. The tool of claim 6 wherein the outer layer is hardened by a process which produces a gripping element having graduated hardness, the hardness of succeeding gripping element layers being inversely correlated to each layer's distance from the outer layer, the core being the softest portion of the gripping element.
 8. The tool of claim 6 wherein the outer layer is case hardened by a nitriding, carbonitriding or carburizing process which leaves the hardness of the middle of the core materially unaffected.
 9. The tool of claim 1 wherein the hardness of the outer layer is in the range of 75-90 HR 15 N.
 10. The tool of claim 1 wherein the hardness of the outer layer is in the range of 75-90 HR 15 N.
 11. The tool of claim 1 wherein the gripping element is comprised of MPIF/ASTM F-0000.
 12. The tool of claim 1, wherein at least some of the gripping elements are wickers having a hardened outer layer, wherein the outer layer is case hardened by a nitriding, carbonitriding or carburizing process which leaves the core materially unaffected.
 13. The tool of claim 1, wherein at least some of the gripping elements are inserts having a hardened outer layer, wherein the outer layer is case hardened by a nitriding, carbonitriding or carburizing process which leaves the core materially unaffected.
 14. The tool of claim 1, wherein the tool may be milled out of the casing in 50% or less time than needed to mill out a similar tool in which of the similar tool's gripping elements are carbide.
 15. The tool of claim 1 wherein, upon milling the tool out of the casing, the largest 10% of the cuttings produced by the milling are at least 30% smaller than the largest 10% of the cuttings produced by milling out a similar tool with carbide inserts under similar conditions.
 16. A settable downhole tool comprising: a mandrel; and a slip located about the mandrel for engaging a casing and holding the tool to the casing; wherein the slip is comprised of one or more slip bodies and multiple gripping elements, the slip bodies holding the gripping elements; at least some of the gripping elements are: made from compacted powdered iron having up to 0.3% by weight carbon, and have an outer layer and a core, the outer layer is for engaging the casing and has been case hardened by nitriding, carbonitriding, or carburizing to be harder than the core and has a hardness in the range of 70-97 HR 15 N (superficial Rockwell); and the core is for supporting the outer layer against the casing, and has hardness in the range of 12-60 HRB (Rockwell); and wherein the tool, after being set in the casing, may be milled out of the casing in 50% or less time than needed to mill out a similar tool in which of the similar tool's gripping elements are carbide.
 17. A method of making the settable downhole tool of claim 15 comprising: providing a mandrel; providing a slip for being located about the mandrel for engaging a casing and holding the tool to the casing; wherein the slip is comprised of one or more slip bodies and multiple gripping elements, namely, wickers or inserts, the slip bodies holding the gripping elements; providing at least some gripping elements manufactured from a single material; namely compacted powdered iron with up to 0.3% by weight carbon, and have an outer layer and a core, the outer layer being for engaging the casing and has been hardened by nitriding, carbonitriding or carburizing to be harder than the core and have hardness in the range of 70-97 HR 15 N (superficial Rockwell); and the core is held by a slip body, is for supporting the outer layer against the casing, and has hardness in the range of 12-60 HRB (Rockwell); wherein the gripping element is hardened by a process which produces a gripping element having graduated hardness, the hardness of succeeding gripping element layers being inversely correlated to each layer's distance from the outer layer, the core being the softest portion of the gripping element; and assembling the mandrel, slip and gripping elements to make a tool which may be milled out of the casing in 50% or less time than needed to mill out a similar tool in which of the similar tool's gripping elements are carbide.
 18. A settable downhole tool comprising: a mandrel; and a slip located about the mandrel for engaging a casing and holding the tool to the casing; wherein the slip is comprised of a unitary body having multiple gripping elements on the slips outer surface; wherein: the slip is made from compacted powdered iron having up to 0.3% by weight carbon, and has an outer layer and a core, the outer layer is for engaging the casing and has been case hardened by nitriding, carbonitriding or carburizing to be harder than the core and has a hardness in the range of 70-97 HR 15 N (superficial Rockwell); the core is for supporting the outer layer against the casing and has hardness in the range of 12-60 HRB (Rockwell); and the slip has one or more relatively thin sections which extend from the upper end of the slip to the lower end of the slip for preferentially breaking at the thin sections as the slip is expanded when the tool is set in the casing.
 19. A settable downhole tool comprising: a mandrel; gripping element; a packing element; wherein the slip comprises a gripping element comprising compacted powdered metal having a core and an outer layer, wherein the core has a hardness in the range of 12-60 HRB (Rockwell) and is a softer material than the harder outer layer.
 20. The downhole tool of claim 19, wherein the slip includes a slip body and wherein the gripping element comprises multiple powder metal buttons engaging the slip body.
 21. The downhole tool of claim 20, wherein at least some of the buttons are cylindrical, with a length of between 0.25″ and 0.375″ and a diameter of between 0.350″ and 0.400.″
 22. The downhole tool of claim 20, wherein the powdered metal buttons are low or no carbon iron.
 23. The downhole tool of claim 20, wherein the harder outer layer is carbonitrided.
 24. The downhole tool of claim 20, wherein the harder outer layer has a hardness in the range of 70-97 HR15N (superficial Rockwell).
 25. The downhole tool of claim 20, wherein at least one of the slip body, packing element, cone or mandrel is made, at least partly, from a material degradable in a downhole fluid.
 26. The downhole tool of claim 20, wherein at least one of the slip body, packing element, cone or mandrel is made, at least partly, from a millable material.
 27. The downhole tool of claim 20, wherein at least one of the slip body, packing element, cone or mandrel is made, at least partly, from a millable non-metallic material comprising a composite material.
 28. The downhole tool of claim 20, wherein the harder outer layer is between 0.005″ and 0.040″ thick.
 29. The downhole tool of claim 20, wherein the core has a hardness in the range of 12-60 HRB (Rockwell).
 30. The downhole tool of claim 19, wherein the slip includes a slip body and wherein the gripping element comprises a multiplicity of powder metal wicker pads.
 31. The downhole tool of claim 30, wherein the powdered metal wicker pads are low or no carbon iron.
 32. The downhole tool of claim 30, wherein the harder outer layer is carbonitrided.
 33. The downhole tool of claim 30, wherein the harder outer layer has a hardness in the range of 70-97 HR15N (superficial Rockwell).
 34. The downhole tool of claim 30, wherein at least one of the slip body, packing element, cone or mandrel is made, at least partly, from a material degradable in a downhole fluid.
 35. The downhole tool of claim 30, wherein at least one of the slip body, packing element, cone or mandrel is made, at least partly, from a millable material.
 36. The downhole tool of claim 30, wherein at least one of the slip body, packing element, cone or mandrel is made, at least partly, from a millable non-metallic material comprising a composite material.
 37. The downhole tool of claim 30, wherein the harder outer layer is between 0.005″ and 0.040″ thick.
 38. The downhole tool of claim 29, wherein the wicker pad has arms for engaging the slip body.
 39. The downhole tool of claim 29, wherein the wicker pad has dovetail side walls for engaging the slip body.
 40. The downhole tool of claim 30, wherein the core has a hardness in the range of 12-60 HRB (Rockwell).
 41. The downhole tool of claim 19, wherein the gripping element is a powder metal wicker.
 42. The downhole tool of claim 41 wherein the powdered metal wicker is low or no carbon iron.
 43. The downhole tool of claim 41, wherein the harder outer layer is carbonitrided or borized
 44. The downhole tool of claim 41, wherein the harder outer layer has a hardness in the range of 70-97 HR15N (superficial Rockwell).
 45. The downhole tool of claim 41, wherein at least one of the slip body, packing element, cone or mandrel is made, at least partly, from a material degradable in a downhole fluid.
 46. The downhole tool of claim 41, wherein at least one of the slip body, packing element, cone or mandrel is made, at least partly, from a millable material.
 47. The downhole tool of claim 41, wherein at least one of the slip body, packing element, cone or mandrel is made, at least partly, from a millable non-metallic material comprising a composite material.
 48. The downhole tool of claim 41, wherein the harder outer layer is between 0.005″ and 0.040″ thick.
 49. The downhole tool of claim 41, wherein the core has a hardness in the range of 12-60 HRB (Rockwell).
 50. A slip for a downhole tool, the slip comprising: a gripping element comprising compacted powder metal, the gripping element having a hard outer layer for gripping a tubing and core supporting the outer layer and having hardness in the range of 12-60 HRB (Rockwell).
 51. The slip of claim 50, wherein the gripping element is a powder metal button and the slip includes a slip body.
 52. The slip of claim 50, wherein the gripping element is a powder metal wicker pad and the slip includes a slip body.
 53. The slip of claim 50, wherein the gripping element is a powder metal wicker.
 54. The slip of claim 51, wherein the powdered metal buttons are low or no carbon iron.
 55. The slip of claim 51, wherein the harder outer layer is carbonitrided.
 56. The slip of claim 51, wherein the harder outer layer has a hardness in the range of 70-97 HR15N (superficial Rockwell).
 57. The slip of claim 52, wherein the powdered metal buttons are low or no carbon iron.
 58. The slip of claim 52, wherein the harder outer layer is carbonitrided.
 59. The slip of claim 52, wherein the harder outer layer has a hardness in the range of 70-97 HR15N (superficial Rockwell).
 60. The slip of claim 53, wherein the powdered metal buttons are low or no carbon iron.
 61. The slip of claim 53, wherein the harder outer layer is carbonitrided.
 62. The slip of claim 53, wherein the harder outer layer has a hardness in the range of 70-97 HR15N (superficial Rockwell). 